Some multi-band or other tactical radios operate in the high frequency (HF), very high frequency (VHF) (for satellite communications), and ultra high frequency (UHF) bands. The range of these multi-band tactical radios can operate over about 2 through about 512 MHz frequency range. Next generation radios will probably cover about 2.0 to about 2,000 MHz (or higher) to accommodate high data rate waveforms and less crowded frequency bands. This high frequency transmit mode is governed by standards such as MIL-STD-188-141B, while data modulation/demodulation is governed by standards such as MIL-STD-188-110B, the disclosures which are incorporated by reference in their entirety.
UHF standards, on the other hand, provide different challenges over the 225 to about 512 MHz frequency range, including short-haul line-of-sight (LOS) communication and satellite communications (SATCOM) and cable. This type of propagation can be obtained through different weather conditions, foliage and other obstacles making UHF SATCOM an indispensable communications medium for many agencies. Different directional antennas can be used to improve antenna gain and improve data rates on the transmit and receive links. This type of communication is typically governed in one example by MIL-STD-188-181B, the disclosure which is incorporated by reference in its entirety. This standard specifies a family of constant and non-constant amplitude waveforms for use over satellite links.
The joint tactical radio system (JTRS) implements some of these standards and has different designs that use oscillators, mixers, switchers, splitters, combiners and power amplifier devices to cover different frequency ranges. The modulation schemes used for these types of systems can occupy a fixed bandwidth channel at a fixed carrier frequency or can be frequency-hopped. These systems usually utilize memoryless modulations, such as a phase shift keying (PSK), amplitude shift keying (ASK), frequency shift keying (FSK), quadrature amplitude modulation (QAM), or modulations with memory such as continuous phase modulation (CPM) and combine them with a convolutional or other type of forward error correction code. Standard waveforms are often used.
These different waveforms and equipment in the joint tactical radio system typically use a software-defined radio (SDR) that follows the open architecture framework defined by the software communications architecture (SCA), which provides the framework for how the hardware and software in the software-defined radio operate. The SCA is a key element of the JTRS and allows programmable radios to load waveforms, run applications and network into an integrated system using a core framework as a standard operating environment that is implemented on every hardware radio. The same waveform software can be ported to all radio sets.
Some current software-defined radios use a lossy, non-volatile storage medium such as NAND memory, which relies on the ability to erase and rewrite a block when an error correction code (ECC) or “soft” failure occurs. This is necessary to prevent a non-recoverable failure on a subsequent read. If the write enable pin of the storage medium, for example, the chip memory, is disabled by a third party outside the control of the normally used driver, the wear leveling correction sequence should be deferred. Therefore, a technique is required to prevent data loss in these circumstances.